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I have been on the FI section of this forum for awhile and now that I have had IPT do a complete upgrade on my ZF auto, I am now getting transmission error lights which Buckhead Import Performance says has to do with the traction control. BIP says that they have not found anyone who programs the TCU (no, not even IPT) in order to fix this glitch. The car runs fine until I punch it to carry more speed thru a big sweeper, the transmission light comes on and it goes into a partial limp mode - shifts when it should but very hard, I turn it off, wait a minute and restart which clears it. Until I do any power acceleration with the car in a curve.
Who can I go to to fix this computer glitch in my TCU programming?

Trying to learn more about this issue, I first pressed the DSC button to turn it off (just the triangle light) and made a hard run. Transmission light came on and it went into the partial limp mode which I cleared. Next, I pressed the DSC button and held it down until both the triangle and brake lights came on. I again made a hard run and the transmission light came back on with the resulting partial limp mode - I cleared this.
I am told that there is a traction control module in the engine bay that I can disconnect and still drive the car. Will this do anything more than what I have already done?

what does this error light look like? does it have the circle around the "!"? i've had my rehauled ipt tranny for years now, and i've never had a tranny related issue.... i did have the "!" when my tune was off.

I have been running 255/35-18's on the front and 275/35-18's on the rear for over four years with no problem whatsoever. This error code started appearing AFTER I got back the IPT rebuilt transmission. Jason @BIP suspects that the power now going thru the transmission is overwhelming the TCU. Since the rears were about worn out I have just replaced them with smaller 265/35-18's to see if the tire size has any effect - nope. Somehow the TCU has to be programmed to be more tolerant of the new power.

I think the tire size difference may be the issue, not the traction control. One way to test this is to borrow a set of "square" tires to try on your car.

Your existing front has a roll-out of 78.6 inches, and the rear 79.5 inches. Technically this would be "Under-slip", or a negative slip value. I'm not sure how the traction control map is set up with MS45.1, but on race cars we use a different slip allowance for corners than in a straight line. The reason is that the side loading on the tire reduces the longitudinal grip resulting in say a 5% rate of slip being optimal in a corner versus say 15% when going in a straight line. BMW may have this mapped based on torque output from the engine, steering angle as well as rate of change of steering angle, G force, and finally wheel slip as a feedback mechanism. Changing the torque output value, or allowed value, may help you hide the difference in wheel speed causing the feedback loop to trigger an error, but it won't give you optimal traction control.

If you don't have access to another set of wheels, I would consider changing your front tire to a 235/40/18. (79.8" roll out)

Trying to learn more about this issue, I first pressed the DSC button to turn it off (just the triangle light) and made a hard run. Transmission light came on and it went into the partial limp mode which I cleared. Next, I pressed the DSC button and held it down until both the triangle and brake lights came on. I again made a hard run and the transmission light came back on with the resulting partial limp mode - I cleared this.
I am told that there is a traction control module in the engine bay that I can disconnect and still drive the car. Will this do anything more than what I have already done?

Any help will be much appreciated.

TIA,
Jim

I just disconnected the module next to the master cylinder. First reaction is that the following has happened:
1. Speedometer is not working along with the MPG gauge
2. These lights are now on - traction control, brake, ABS and TPMS.

Driving is fine and the transmission shifts fine as well. The car feels a little edgy as I now have to adjust to any difference in surface grip. I can now
"peel out" from a standing start with not much throttle as both rear tires are controlled by my OS Giken LSD.
Later, after several hard run attempts I finally got the transmission light to come on and go into the partial limp mode - I stopped and cleared it.
My conclusion is that it now takes more to get the transmission light to come on. What does this mean?

I think the tire size difference may be the issue, not the traction control. One way to test this is to borrow a set of "square" tires to try on your car.

Your existing front has a roll-out of 78.6 inches, and the rear 79.5 inches. Technically this would be "Under-slip", or a negative slip value. I'm not sure how the traction control map is set up with MS45.1, but on race cars we use a different slip allowance for corners than in a straight line. The reason is that the side loading on the tire reduces the longitudinal grip resulting in say a 5% rate of slip being optimal in a corner versus say 15% when going in a straight line. BMW may have this mapped based on torque output from the engine, steering angle as well as rate of change of steering angle, G force, and finally wheel slip as a feedback mechanism. Changing the torque output value, or allowed value, may help you hide the difference in wheel speed causing the feedback loop to trigger an error, but it won't give you optimal traction control.

If you don't have access to another set of wheels, I would consider changing your front tire to a 235/40/18. (79.8" roll out)

As I mentioned above, I have been running the 255/35F and 275/35R for many years now with no trouble at all. And the post right above this one where I still get the transmission light even though the traction control module has been disconnected. What is the next step?

Were you able to rev the engine above 5200 RPM with the brake module disconnected?

If you were able to rev above 5200 RPM, I would suggest to try disconnecting the left rear wheel speed sensor. If you are unable to rev above 5200 RPM with this sensor disconnected, and the brake module disconnected, the speed signal used by the TCU is coming from somewhere else.

I've experienced an RPM limit across a few models and brands when the rear left speed sensor signal is absent. I think it may have something to do with OBD and an automaker's legal obligations.

Were you able to rev the engine above 5200 RPM with the brake module disconnected?

If you were able to rev above 5200 RPM, I would suggest to try disconnecting the left rear wheel speed sensor. If you are unable to rev above 5200 RPM with this sensor disconnected, and the brake module disconnected, the speed signal used by the TCU is coming from somewhere else.

I've experienced an RPM limit across a few models and brands when the rear left speed sensor signal is absent. I think it may have something to do with OBD and an automaker's legal obligations.

Just ran it in first gear to the redline and the transmission light came back on.